Hydraulic brake



July 18, 1939.. E. F. LowEKE HYDRAULIC BRAKE Filed. Dec. 3o,I 1931 u v .m

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Patented July 18, 1939 HYDRAULIC BRAKE Erwin F. Loweke, Detroit, Mich., assigner to Hydraulic Brake Company, Detroit, Mich., a corporation of California Application December 30, 1931, Serial No. 583,875

9 Claims.

My-invention relates to hydraulic brakes, and is particularly concerned with the means for insuring exclusion of air from the operating parts of hydraulic brake systems. As will be readily 5 appreciated, it is of the utmost importance thatl air and other gases be excluded from the operating parts of hydraulic brake systems if the brake system is to be maintained in proper operating condition. One of the commonest points for air l to enter a hydraulic brake system is in rear of the master cylinder and one of the objects oi my invention is to improve the construction of the brake system at this point so as to eliminate any possibility of air leaking into the system at l this point.

Another object of my invention is to accomplish the foregoing result in the simplest and most economical manner.

Another object is to provide a iluid seal for hydraulic brake systems which is always maintained under super-atmospheric pressure.

Another object is to reduce to a minimum the area through which air might gain access to the system.

Other objects and ladvantages will be apparent as the description proceeds.

In the drawing,

Fig. 1 is a view of the principal elements of a hydraulic brake system, showing certain parts in section better to illustrate the construction thereof;

Fig. 2 is a fragmentary view in section showing a modied form of my invention; and i Fig. 3 is a section taken on the line 3--3 of 35 Fia 2.

Referring to Fig. 1 of the drawing, I have i1- Y lustrated a hydraulic brake system as ,comprising a reservoir I, a master cylinder 2, and a motor cylinder 3. The reservoir I is commonly mounted on the dash 4 of a motor vehicle and is provided with either a small open vent or more preferably, .valve mechanism such as indicated at 5, to maintain the reservoir under substantially atmospheric pressure. The valve mechanism 5 is not disclosed in full herein, since this valve mechanism is fully illustrated and described in the application of Clarence V. Gardner, Serial No. 535,316 filed May 6, 1931, now Patent No.

The reservoir I is connected by a.' pipe S with a boss 'l integral with the master cylinder 2. The master cylinder 2 comprises acompression cylinder 8 of relatively large diameter, in which is reciprocably mounted a piston 9, adjacent -the forward face of which is located #rubber cup I0.

(Cl. Bil-54.6)

'I'he piston 9 and cup III 'are advanced by a pin II which simply rests in a socket in the rear face of the piston 9, and which is separable therefrom.

The other end of the pin II is pivotally connected to an operating lever I2 pivoted at I3 to 5 a bracket I4 which is amxed to the frame of the vehicle in any suitable manner. The lever I2 is actuated in brake applying direction by the hand or foot of the driver or by suitable power means where so desired. This lever I2 is returned to 10 normal position by a suitable springwhich is indicated at I5.

The rear end of the master cylinder is provided withan integral tubular extension I6 which may be suitably attached either to the bracket I4 or 15 directly to the vehicle frame. A exible boot I1 of leather, rubber or other suitable material closes the end of this extension against the entry of dirt or moisture. The piston 9 is provided with-a reduced rearward extension I8 lwhich re- 2o ciprocates in the tubular extension I6. 'Ihe extension I8 provides an annular chamber I9 which is filled with liquid and which serves as a liquid v seal -for preventing the entry of air into the brake system. The extreme rear of the extension I8 25 carries a flexible packing 20.

The fcup I0 is held against the forward face of the piston 9 by a spring 2| whichfunctions to re'- turn the piston and cup to retracted position at the termination of brake application, and which also functions to hold against its seat a return valve 2 2 located at the discharge end of the compression cylinder 8. The return valve 22 carries a centrally located outlet valve 23 which is lightly held in closed position by a spring 24. A small -port '25 connects the compression cylinder 8 with the-condut when the piston il and cup Ill are 'in the retracted position as shown in Fig. l of 'the drawing.

`Achamber I9. The rear edge of the piston s isv chamfered as indicated at 2l, thereby providing a small-annular space at the extreme rear end of the part which forms the compression cylinder 8, and the port 26 also connects with this ann nular space. The piston 9 is provided with passages 28 which permit iiow of iiuid therethrough during the return stroke of the piston. During the return stroke of the piston'the forward edge 50 of the cup It collapses to permit flow of duid there past, and the base portion of the cup is provided with axial grooves 2 9 which facilitate flow of fluid past the heavy base of the cup during the return stroke of the piston.

Fluid discharged from the compression cylinder 8 llows through a conduit Sii to the motor cylinders 3, which are most commonly located at the vehicle wheels, although these motor cylinders and attendant mechanisms are equally ce.- pable of use on the propeller shaft of the ve hicle, or on the axles at points spaced from the vehicle wheels or in any other suitable location on the vehicle chassis.

In the drawing I have illustrated the motor cylinder 3 as secured to a pan El attached to the axle housing 32. provide a section of flexible conduit 3d to accommodate the relative motion between the motor cylinder il and the master cylinder 2. The motor cylinder .'.i has opposed pistons 34, each provided with a rubber cup 2b'. The cups are held against the piston iaces by a relatively light spring Each piston 34 is connected with a brake shoe 3l by a pin 28 which simply rests in a socket in the back of a piston 34. The ends of the motor cylinder 3 are closed against entry of dirt and water by flexible caps 39 A of rubber or other suitable material.

fluid. The uid in the conduits 20 and motor The brake shoes 3l are mounted on pins dll afxed to the pan 3l. Each shoe is provided with suitable guides 4I and a relatively strong retractile spring 42 which holds its shoe against a suitable stop indicated at dit. Each shoe is provided with brake lining 44 :for engaging the brake drum 45 which is attached to the 'vehicle wheel or other rotating element.

The operation of this enibodinient'of my invention is as follows. In the position of the parts shown in the drawing, which .is the normal position of these parts, the reservoir is partly lled with fluid and the cylinders 3 and 8, conduits 5 and 30 and sealing chamber I 9, are illled with cylinders 3 is under a pressure approximating nine pounds above atmospheric pressure, which is maintained by the returnfvalve 22. The fluid in the compression cylinder 8 and chamber I9 is maintained under a pressure supply above atmospheric pressure due to the elevation of the reservoir I, which is usually located approximately two feet above the master cylinder 2, so that the pressure in the compression cylinder and iluld seal approximate one pound above atmospheric pressure. 'When the lever I2 is moved to apply the brakes, the cup III first moves to a. position to close the port 25, after which the pressure in the compression cylinder 8 increases as the cup Il and piston 9 advance. The advance of the cup 'I0 and piston 9 forces fluid through the outlet valve 2l and into the conduits 30, whence iluid is forced into the motor cylinders 3. This spreads the motor pistons I4 and applies the brake shoes 31 against the brake drum 45.

When the force exerted on the lever I2 is released, the spring I5 returns this lever to normal position independently of the piston 9. The outlet valve 23 closes and the'spring 2| returns the piston 9 and cup I0 to the position shown in the drawing.

The return movement of the piston I Il and cup 9 is faster than the return of uid from the-motor cylinders, since the return valve 22 and the long and small diameter conduits 3l retard the return now of uid from the motor cylinders to the compression cylinder. Thus a. vacuum or condition of sub-atmospheric pressure is created ln the compression cylinder during the return stroke of the piston 9 and cup I9, and during this return movement fluid iows through the passages encarar 2G in the piston El post the cup` lll and thence into the compression cylinder t3.'

Since the bore of the compression cy er l is larger than the bore of the extension a certain amount of fluid must be displaced behind the piston 2 during its return stroke. lart of this fluid try-passes the piston and cup, as previously/explained, and thus `finds its way into the compression cylinder Il. The remainder of this huid is forced baci: into the pipe G through ports 25 and 2S. and retard the returnV flow of this iluid so that a pressure is created on the iluid inthe chamber lil. This pressure in the sealing chamber i9 absoN lutely prevents the entry of any air past the gasket 20 during the return stroke of the piston.

When the piston 9 and cup I0' reach their fully retracted position, the port 25 establishes coinmunication between the reservoir and the compression cylinder Il. There is now an excess o3 fluid in the compression cylinder, conduits 'im and motor cylinders 3 and as the pistons 3d oil the motor cylinders complete their return strolres,

this excess of fluid is discharged through the port 25, and carries with it any air which may have crept into the motor cylinders, conduits Bil compression cylinder' 8.

In the modiiication shown in Figs. 2 3, the boss l of the master cylinder 2' provides a shoulder on which is located a valve mechanism 5B. This valve mechanism 5|) comprises a seat member 5I and a disk 52 provided with a small lcentral opening 53 and guide fingers 54. This valve means 50 is interposed between the conduit 6 leading to the reservoir and the port 25' which communicates with the compression cylinder 8', which is identical with the compression cylinder 8 previously described. In this compression cylinder l' are located the piston 9, cup Il, spring 2|, etc., all as previously described.

'I'he valve mechanism 55 is also interposed between the conduit 5 andV the port 25' which communicates with the chamber I9 formed in the periphery of the rearward extension I9 of the piston 9. In this embodiment the port 25' may be made larger than the port 25 ofthe previous embodiment shown in Fig. 1. The valve disk 52 is normally held in the position shown in Fig. 2 by the force of gravity. In this position the ilnge'rs 54 rest on the shoulder formed in the boss 2' and uid may readily pass from the reservoir around the edges of the valve disk 52 and thence through ports 25 and 25'.

During the return stroke of the piston the uid behind the piston rushes up through the port 25' and lifts the valve disk 52 against its seat 50, thereby restricting the passageway leading back .to the reservoir to the small opening 53 through the valve disk. This restriction on the return of fluid to the reservoircreates a superatmospherio pressure in the chamber I! and maintains this pressure throughout the return stroke of the piston.

As in the previous embodiment, part of the duid behind the piston by-passes the piston and cup and thus reaches that part of the compression cylinder in front of the cup Il. As soon as the piston has completed its return stroke the disk 52 drops to the position shown in Fig. 2.

In this embodiment, the port 25' may be made relatively large so as to provide free communication between the'reservolr and the rear of the piston during the forward motion of the piston and thus prevent the creation of a vacuum in the rear of the piston during its forward motion.

Both of these ports are small The passageway 53 through the valve disk 52 is preferably made larger than the port but considerably smaller than the port 26'.

While I have lillustrated and described two embodiments ofzm'y invention, it is to be understood that my invention is capable of assuming various other forms and that my invention is limited solely by the scope of the following claims.

I claim:

l. In brake mechanism of the class described, the combination of'a compression cylinder havin g a discharge outlet, a -piston in said compression cylinder, a spring for returning said piston, a tubular extension in rear of said compression cylinder, said tubular extension having a bore less than that of the compression cylinder and forming a stop for said piston, a sealing part integral with said piston and extending into said tubular extension, said sealing part provided with an annular chamber cooperating with the bore of said extension, a reservoir communicating with said compression cylinder and chamber, a restriction valve between said reservoir and chamber cooperating with said piston to create pressure in said chamber during the return stroke of said piston, and a cup washer associated vwith said piston to permit ilow of fluid from said extension into said cylinder.

2. In apparatus of the class described, the combination of a compression cylinder having a discharge outlet, a piston reciprocable in said compression cylinder, said piston having a rearward extension of reduced diameter and said compression cylinder having. a rearward tubular extension of reduced diameter into which the extension on said piston projects, said rearward tubular extension forming a continuation of said compression cylinder, said extensions providing a chamber therebetween forming a iluid seal for said compression cylinder of less diameter than the diameter of said piston whereby a pressure is created therein by the rearward extension of said piston during the return stroke of said piston, said fluid seal constituting a continuation of the chamber of said compression cylinder, and a iluid reservoir communicating with said seal.

3. In apparatus of the class described, the combination of a cylinder having a discharge outlet, a piston reciprocable in said cylinder, means for advancing said piston to create a pressure in said cylinder, a spring for returning said piston, a valve interposed between said outlet and said compression cylinder, a chamber of reduced diameter forming al continuation of said 'compression cylinder -in rear of said piston,

4 iiid past the piston in one direction only, a chamber forming a seal for preventing leakage al past saidv piston during the return stroke' thereof, a fluidv reservoir, a single connection be tweensaid duid reservoir 'and said seal, a second connection between said fluid reservoir and that part of said cylinder in front o! said piston, and means including said piston and a valve in said first-mentioned connection for creating pressure in said fluid seal during the return stroke of said piston and for forcing iluid fromsaid seal past said piston and into said compression cylinder.

5. In apparatus of the class described, the combination of a compression cylinder, a piston reciprocable therein, a fluid reservoina conduit in communication with said reservoir, a port connecting said conduit to that portion of said cylinder in front of the retracted position of said piston to permit return iiow o! iluid from said cylinder to said reservoir, a fluid chamber in rear of said piston, a second port connecting said chamber with said conduit whereby iluid may flow from said reservoir into said chamber, said first port being smaller than said second port, and valve means in said conduit openable to permit free flow from said reservoir through said conduit to said ports, said valve means including a part having a passageway therethrough of less diameter than said second port, said passageway limiting return iiow oi iiuid from said second port to said reservoir.

6. In a device of the class described, the combination of a compression cylinder, a piston reciprocable therein, said piston having a rearward extension of reduced diameter, said compression cylinder having a rearward tubular extension of reduced diameter into which the extension on said piston projects, said rearward tubular extension constituting a continuation of the chamber formed by said compression cylinder, said extensions providing therebetween an annular chamber constituting a continuation of said cylinder and forming a iiuid seal for said compression cylinder and being cooperable to build up a pressure in the iiuid seal during the return stroke of the piston, a fluid reservoir, a single means of communication between said reservoir and said seal, and a ilow restriction in said lastmentioned means.

7. In ahydraulic pressure system of the class described, the combination oi.' a pair of interconnected different diametered cylinders, a pair of interconnected diierent diametered pistons reciprocable in said cylinders, the smaller of said pistons cooperating with the smaller of said cylinders to provide an annular chamber constituting `a continuation of the chamber provided by the larger of said cylinders, means for reciprocating said pistons, a reservoir, a connection between said reservoir and each of said cylinders, and a restriction valve in the connection between said reservoir and the smaller o! said cylinders permitting free ilow from said reservoir to said cylinder and limited return flow through said connection.

8. In a iluid pressure mechanism, a cylinder, a piston reciprocable therein, a reservoir, means forming a passage between the reservoir andthe cylinder, said passage being uncovered by the piston in its retracted position, a. iluid containing chamber at the rear of the piston the volume of winch varies with the piston movement, means forming a passage between the reservoir and the chamber, means permitting iiuid to iiow from said chamber past thepiston on its return stroke, and valve means i'orsaid passages for allowin iiuid to'ow therethrough in one direction when the fluid pressure in that direction is a given value andin the other direction when the pressure in said direction is of lower value.

4 escama- 9. In a fluid pressure mechanism, a @y1-mler, a piston reciprocable therein, a reservoir, means forming a passage between the reservoir and the cylinder, said passage being uncovered by the piston in its retracted position, a uid containing chamber at the rear of the piston the voume ot which varies with the piston movement, means forming' n passage between the resewor :um the chamber, means permitting fluid to ow from said chamber past the piston on its return stroke, and valve means fpr said passages for allowing fluid to flow from said reservoir therethrough at a predetermined pressure and in the opposite direction when the pressure in said direction is of greater mine.

ERWN F. LOWEKE, 

